(CARB) Nikki Idle Problems
 

I saw a thread the other day on tuning the nikki something about turn the mixture screw until the engine stumbles then turn the idle down then keep repeating until you get the idle down or something like that. Can anyone send me the thread in case im missing something.

Thanks in Advance
Edward

it's in the FAQ section.

Search for "Sterling"

pretty much just get it too 7-800 RPM's and call it good.

Or you can compete with some of the old guys too see who can get the lowest idle. I used to idle evenly at 550, but always wondered if it would be there when I pulled into traffic.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/sa-compared-sti-714621/

It's in the FAQ page under Sterling's threads.

Well I don't F$#&^@NG know! I have a vacuum leak or the engine is hurt(Don't know the exact status of the engine since it was not running when it was brought to the house). I can not get it under 1000-1500 it starts to stumble by about 300 RPM when you get that low. I removed the rats nest, new intake and exhaust gaskets. I cleaned the intake but there could be some shit on it so I don't get a good seal. Put my cap and rotor, plug wires and 2nd gen plugs to get it running. thinking about taking fan off so I can get a good spray with the carb cleaner to look for leaks.

The statement about rpm is fine until you toss in the 300#, then it gets confusing. It should be stumbling by 5-600 if you have no vac leaks. If you're having trouble setting idle below 1000 rpm, you're on the right track checking for vac leaks. No need to remove the fan, you could easily overheat the engine. If you're using carb cleaner, insert the spray straw into the nozzle, this allows one to pinpoint leaks easier and less blowing around of the spray from the fan.

Don't take the earlier post about setting the idle at 550 rpm too seriously. Sterling is very proud of his modded carbs that will idle in that range, but it's rare that a stock carb will.

damm im having troble just getting it to idle at 1500 0r 1000 it stays at 3000

Yeah... I've got a Sterling and let me tell you, it takes some getting used to the fact that it's OKAY for the needle to drop below 1k because that thing is rock solid around 550-600rpm. For the first while when I drove it I kept panicking when it went below 800 because I thought it was going to die, but nope, if you let it go it just stops falling and idles so low and smooth you can barely hear it.

I love it :D

Jon

If you're having trouble getting it to idle (definition of idle is being in the idle circuit on the carb which only happens at 900rpm and below) then you have to check for vac leaks first and foremost. They're such a bugger to track down, but if you have the chance the easiest way to start eliminating vac leaks is to take the rat's nest out.

When troubleshooting vac I usually do this:

Take out the rat's nest. Hook the two vacuum advance pots to a "T" and hook it to the 2nd port on the spacer. Block off everything else with proper sized vacuum caps. Check that the Anti-Afterburn Valve's hose isn't cracked and is securely attached to its large vac port on the back of the manifold. Make sure to cap the shutter valve.

If it won't idle with that, then it's time to get dirty. The ACV comes off in favor of a block-off plate, the AAB comes off and I cap the vac source at the back of the manifold. I remove the shutter valve and JBWeld the vac holes for it. I double-check the vac brake booster line and put it all back together.

If THAT doesn't work, I try a different carb (they're easy to swap at this point with all the stuff removed). Then I take the intake and carb off and work my way slowly forward. I figure the engine can't vac leak itself, so if I check every point while putting it back together I'll eventually find it.

Sources of vacuum leak starting at the engine:

- Engine-to-manifold gasket
- Air Control Valve or ACV Block-off plate
- Vacuum source for Anti Afterburn Valve
- Vacuum source for vac brake booster
- Big black vac nipple (capped stock) near where shutter valve was
- Shutter valve or its associated vac holes
- Manifold-to-spacer
- Vacuum nipples on spacer
- Spacer to carb
- Vac ports on carb (should be 2-3 on either side I believe, plus extras at the top by the alt compon late models)


So between that list and swapping carbs, there's not a single idle problem you can't fix that I know of. Oh yeah, throttle cable. Make sure it's not too loose, or even un-do it and close the throttle gently by hand with the car running to see if that helps.

Honestly, vac leaks are always the big problem with getting a car to idle (run at or below 900rpm). If vac leaks aren't it, then you need a carb rebuild, or on a rare possibility you've got a fuel problem such as an aftermarket pump with no regulator. A 6psi aftermarket pump will overwhelm a stock carb's needles/seats and flood like hell, but even a car that's flooding can "run" at 2krpm or higher if you can get it started, just not well.

Ask me how I know about idle problems, lol. I spent a LOT of time troubleshooting my first few carbs before the Sterling.

Jon

If at any point in the above process you can get it around 1k rpm, take a minute to adjust your timing, it helps. You've gotta make sure your vac advance pots are hooked up though, so T-them into that line to spot 2 on the carb spacer before adjusting.

It's also important to keep in mind that the idle mix and idle speed screws won't do *anything* until you're idling (below 1krpm). Above that they have absolutely zero effect because you're no longer in the idle circuit on the carb. The idle speed screw can be screwed in far enough to go above 1k, but it usually isn't and can't go much above 1,200 since all it controls is where the throttle stop is.

So don't screw around with the screws trying to fix an idle over 1k. Just set the idle mix screw at 3.5 turns out and don't touch it until you get it to 900rpm or less.

Jon